1. Field of the Invention
The present invention relates to fabrication of implants, more particularly, to fabrication of porous metal-based biomaterial for implant dentistry and bone scaffold by microwave sintering.
2. Description of the Related Art
Over the years, a variety of metals have been used as raw materials for dental or bone implants until titanium was discovered having the inherent properties of osseointegration. As a result, titanium becomes one of the most common metals for dental implants because it displays high strength, excellent corrosion resistance and high strength-to-weight ratio. Today, titanium alloy has been widely used to create dental and orthopedic implants because of its excellent biocompatibility and mechanical properties. Most implants made of titanium alloy are fabricated via conventional powder metallurgy or melting production method.
In addition, with development of implant technology, more materials are found having chemical and biological properties that promote osseointegration, such as hydroxyapatite (HA). Hydroxyapatite is a natural and cost-effective candidate for dental implants due to its biocompatibility and its ability to support the growth of new bone tissue. Furthermore, the human bone is a composite of fibrous protein, collagen, and about 65 wt % of HA. Long-term clinical studies show that HA-coated titanium dental implants have excellent bioactivity.
Another commonly used method to improve the osseintegration of the metal-based implant to surrounding bone is through incorporation of a porous metal surface layer to the surface of the metal implants. This is done to improve the fixation of the implant to bone through in-growth of bone tissues into the porous layer. A common technique for coating a porous surface on the implant is plasma spraying technique, which is used for producing coatings and free-standing parts using a plasma jet. Then, the surface can be chemically etched or sandblasted to increase the surface area and the integration potential of the implant. However, there is a possibility that the coating surface may be loosen or detached from the metal implant.
Another shortcoming of the porous coating, as discussed in U.S. Pat. No. 7,291,012, is that porous surfaces are often a thin coating applied on a metal substrate of the implant. As such, bone surrounding the implant can only grow into the coating layer itself. The surrounding bone cannot grow through the coating and into the metal substrate. The depth of bone growth into the implant is limited to the depth of the porous coating.
While efforts have been made to produce metal-based implants with surface metal porosity, less effort has been made to create porous metal-based biomaterials for production of porous implants. It is therefore an objective of the invention to overcome the shortcomings of the conventional methods by providing a method for rapid fabrication of porous metal-based biomaterial that is lightweight, biocompatible, cost-effective and easy to produce. By taking advantage of the fast processing time of microwave sintering, the biological properties of the sintered compact can be preserved. Also, it is desirable to integrate biomaterial (e.g., HA) into the porous metal-based implant without having to provide a separate coating of a biomaterial.